Electromagnetic device



Jan. 2, 1940. D.D. MILLEP? 2,185,503

. I ELECTROMAGNETIC DEVICE v Fi1ed Jan. 7,1939

)NVENTOR D. D. M/L L ER ATTORNEY Patented Jan. 2, 1940 ES PATEiNTIOFFICE ELECTROMAGNETIC DEVICE Daniel D. Miller, New York, N. Y., assignor to v Bell Telephone Laboratories, Incorporated, New

. York, N, Y., a corporation of New. York fApplication January 7, 1939, Serial No. 249,824

centrally pivoted armature.

I An object of the invention is to'provide in a device of the type above mentioned improvements which will make the device better suited to meet vcertain conditions in service.

A feature of the invention resides in a spring supportfor the armature.

Another featureresides in the yoke structure supported on the cores of the electromagnets.

Another feature resides in an adjustable back- I.

stop for the armature.

Other features reside in the particular struc'- ture and arrangement of the parts in combination.

One application of the invention is explaining the invention.

In the drawing;

Fig-1is a front face view of a telephone ringer embodying the invention;

Fig. 2 is a side View, partly in section and taken on the line 2-2 in Fig. 1; and

structure shown in exploded form.

The electromagnetic device shown centrally pivoted armature 3.

The permanent magnet structure I is made in the form of arectangular frame and comprises two permanently magnetized bars 4 and 5 arranged in parallel spaced relation. A- bar 6 of magnetic material which may be readily drilled and tapped and which will hold, under conditions of long service, a screw thread formedtherein is bridged across ends of the magnetized bars 4 and A plate 1 of magnetic material is bridged across the bars 4 and 5 at the other end of the frame structure. Endportions of the, bar 6 and the plate 1 are securely fastened to. the adjacent ends of the bars 6 and 5 in any manner found convenient for providing a good magnetic path through .the parts. The parts of the permanent magnet struc-- ture are shown for instance as welded together at. the points 8. The bar 6 of magnetic material is drilled and tapped to support a machine screw The screw 9 extends toward the back face of the armature 3 5 at one end of the frame structure.

9 of non-magnetic material.

2 Claims.

in electromagnetic devices commonly known as telephone ringers and is, therefore, shown and described as embodied therein merely for the purpose of in the lieures in the drawing comprises a permanent'magnet structure I, a pair of operating coils 2 and a (or. 175-436)"v and is arranged to serve as an adjustable backstop for one'end portion of the armature. A lock nut l0 is'provided on the screw 9 to hold the screw in adjusted position. The plate I of magnetic material may be an integral part of a 5 bracket on the diverging arm portions l2--l2 of which aresupported spaced bells l3-I3 of the ringer. The permanent magnets are magnetized in the assembly I from the center of plate 1 to arranged in parallel spaced relation within the space defined by the permanent magnet structure The cross l4--l4of' theoperating coils 2-2 are supported on the plate 1 by, means of the screws 15-15 and project toward the bar 6 of 16 the permanent magnetstructure I.

A yoke 16 of non-magnetic material is supported on the unsecured end portions of the cores l4-|4. The yoke l6 comprises two enlarged spaced end portions l 1-H joined by a bridge 20 portion l8. Each of the end portions I! as shown in Fig. 3 is apertur'ed at V I9 to frictionally receive the free end portion ofa core M. The yoke -l6 as above mentioned is madeof nonyoke as will be subsequently explained is used as a fulcrum for the armature 3, the yoke struc- "ture must be substantially strong andrigid. It is common practice to make such parts of brass since this material is sufficiently strong for the 30 purpose and is not magnetic. In the yoke structure I have. made a departure from the usual practice of v simplyproviding round apertures in the end portions to receive end portions of the cores ofthe operating coils. In the yoke struc- 35 tureI have devised, an elongated aperture 20 isprovided in the bridge portion l8. The aperture 20 extends longltudinallyof the bridge portion l8 and through portions of the enlarged end the apertures |9l9.' This makes the end por-. tions lI-ll incomplete rings at the unsupported ends of the cores. I l-I4 and reduces eddy currenteffects in the device. Lugs Zl-Zl are provided on the bridge portion 18 to serve as fulcrum points for the armature structure.' The lugs 2l-2l are in register with each other and 'extend downwardly from the plane of the lower face "of the yoke l6 and are located on opposite sides of the bridge portion I8. The lower ends of the lugs 2l-2l are made rounded to provide good rocking points for the armature 3.

The armature 3 is made of magnetic material and is supported by means of a spring 22. The spring 22 in its original form and before being the center of bar 6. The operating coils 2-2 are 10 magnetic material and since a portion of the 25 portions'lL-H and into communication with; 40/

incorporated into the electromagnetic device is substantially flat as shown in Fig. 3, and comprises a central portion 23 and the end portions 24 and 25. The spring 22 may be made of sheet metal or any other material found suitable for the purpose. The end portions 24 and 25 are bifurcated, the paired leg portions 26 and 21 on each end being adapted to pass partially around the apertures E9 in the yoke l5 and being secured to the yoke 16 by suitable fastening means such as the rivets 23. The central portion 23 of the spring 22 is secured to the central portion of the armature 3 by suitable fastening means such as the spaced rivets 29. The spring 22 is interposed between the armature and the yoke and extends longitudinally of the yoke and armature.

The bifurcated formation of the end portions of the spring permits free movementof the end portions of the armature to the ends of the cores of the operating coils. When the leg portions of the spring 22 are secured to the yoke l6 and the central portion of the spring is secured to the central portion. of the armature J, and the yoke I6 is forced into required position on the cores M, the spring 22 takes a bowed formation as shown in Fig. 1.. The deformation of the spring 22 from its original flat condition shown in Fig. 3 to the bowed-formation shown in Fig. builds up sufficient tension. in-the spring 22 to continually urge the central portion of the armature toward the rounded ends of the lugs 2i on the yoke I6. I have found it preferable to have the central portion of the spring 22 wide enough to span the lugs 2|--2l so that the central portion of the spring is interposed between the inner face of the armature and the rounded ends of the lugs 25. This maintains the central portion of the spring in bowed formation. The arrangement also makes the spring take the wear rather than the armature when. the armature is rocked under the influence of the operating coils. I have found that when the ar-- mature 3 is supported by the means above described, the wearing of the parts in service is negligible since as the armature is rocked back and forth, the bowed portion of the spring 22 simply rocks over the rounded end portions of the lugs 2l-2| with comparatively no friction between the engaged parts. The means I have devised for supporting the armature is therefore superior to journal or pin type supports commonly found in devices of the type described and in which there is considerable friction at the points of support and appreciable wearing away of the parts in service. Temperature changes. met in service do not affect the opera-- tion of my device since it contains no pin or journal type bearings in which the associated parts expand or contract under changes in temperature and cause binding or loosening of the engaging parts in the bearing structure. I have also found that the means devised for supporting the armature is superior to reed type spring arrangements which are sometimes twisted beyond their elastic limits and thus are given an abnormal permanent set when the device is dropped to a floor or otherwise roughly handled. The spring in my device is comparatively wide and extends longitudinally of and between the yoke and the armature. It is anchored at each end at rather widely separated points to the yoke and is secured at its central portion to the central portion of the armature by spaced rivets or other suitable fastening means. In the event that the device is dropped to a floor or otherwise subjected to ordinary careless handling, the resulting forces on the spring are distributed over a large area and longitudinally of the spring rather than transversely of the spring and at some concentrated point. p

The device shown for illustrating the invention is a polarized ringer provided with a bias-ing spring 36 and a bell striker. The biasing spring 30 and the bell striker rod 3A are mounted in spaced relation on a lug portion 32 of the armature 3 and extend in parallel spaced relation to the operating coils as well known in the art. The free end portion of the biasing spring may be adjustably placed in notches 33 in a plate 34 of non-magnetic material to obtain the required bias of the armature. The plate 34 is held by means of the screws l5--l5 against the plate i of the magnet structure I. The notched portion of the plate 34 extends beyond the adjacent portion of the plate I. Terminals 35 and 21 provided on the operating coil structure to pe mit the connection of the device to wires of a circuit.

What is claimed is:

1. In an electromagnetic device comprising a pair of electromagnets supported in spacedrelation, an armature operated by means of said electromagnets and a yoke extending across and supported on said electromagnets, spaced projections on said yoke extending normal to the plane of said yoke and a bowed spring secured at its end portions to said yoke and secured at its central portion to the central portion of said armature and pivotally supporting said armature on said projections.

2. In an electromagnetic device comprising a pair of electromagnets supported spaced relation, and a centrally pivoted armature operated by means of said electromagnets, a yoke supported on the cores of said. electromagnets, a spring having its opposite end portions secured to said yoke and a central portion secured to said armature, and projections on said yoke extend-- parallel in parallel ing into engagement with the central portion of said spring and serving as a fulcrum for said armature.

DANIEL D. MILLER. 

